Remote Control of Oceanic Air by Land and its Future Changes
Oceans are well-known to be directly altered by global climate forcings such as greenhouse gas changes, but how oceans are indirectly influenced by land and its response to such forcings remains less explored. Here, we assess the present-day and projected future state of a little-explored feature of the climate system—a ‘land wake’ in relative humidity downwind of the east coast of North America, consisting of low-humidity continental air extending roughly 1000 km over the Atlantic ocean.
The land wake exists throughout the year, in a coastal region is home to numerous large population centers and regions of high marine productivity. As atmospheric carbon dioxide increases, the land wake intensifies in global climate model simulations through two pathways: the radiative effects of carbon dioxide on surface temperatures, and the biogeochemical effect of carbon dioxide on terrestrial vegetation. Vegetation responses to increased carbon dioxide alter the summer wake from Florida to Newfoundland, and both the radiative and biogeochemical effects of carbon dioxide drive reductions in coastal cloud cover. These changes illustrate the potential of rapidly changing terrestrial climate to influence coastal regions and the ocean environment downwind of continents through both light conditions and the energy balance of the surface ocean.
Researchers asked how land influences the state of oceanic air downwind of a continent, using the particular case of the Atlantic Ocean east of North America. They found that enhanced atmospheric carbon dioxide concentrations intensify the wake directly through warming-induced thermodynamic changes and indirectly by altering the rate at which plants emit water vapor into the atmosphere. These changes alter the humidity, light conditions, and surface energy balance in highly productive coastal ecosystems.